Due to advances in computing technology, businesses today are able to operate more efficiently when compared to substantially similar businesses only a few years ago. For example, internal networking enables employees of a company to communicate instantaneously by email, quickly transfer data files to disparate employees, manipulate data files, share data relevant to a project to reduce duplications in work product, etc. Furthermore, advancements in technology have enabled factory applications to become partially or completely automated. For instance, operations that once required workers to put themselves proximate to heavy machinery and other various hazardous conditions can now be completed at a safe distance therefrom.
Further, imperfections associated with human action have been minimized through employment of highly precise machines. Many of these factory devices supply data related to manufacturing to databases that are accessible by system/process/project managers on a factory floor. For instance, sensors and associated software can detect a number of instances that a particular machine has completed an operation given a defined amount of time. Further, data from sensors can be delivered to a processing unit relating to system alarms. Thus, a factory automation system can review collected data and automatically and/or semi-automatically schedule maintenance of a device, replacement of a device, and other various procedures that relate to automating a process.
While various advancements have been made with respect to automating an industrial process, utilization and design of controllers has been largely unchanged. Industrial controllers are special-purpose computers utilized for controlling industrial processes, manufacturing equipment, and other factory automation processes, such as data collection through networked systems. Controllers often work in concert with other computer systems to form an environment whereby a majority of modern and automated manufacturing operations occur. These operations involve front-end processing of materials such as steel production to more intricate manufacturing processes such as automobile production that involves assembly of previously processed materials. Oftentimes, such as in the case of automobiles, complex assemblies can be manufactured with high technology robotics assisting the industrial control process.
Control systems can be employed to control motion related to machines such as robots. Many of these systems include a source that commands motion in a target system. For example, a source (e.g., controller) can be utilized to move a target (e.g., drive, motor, . . . ). Motion control can be effectuated by regularly updating command data sent from a controller to a drive and actual data sent from the drive to the controller. Conventional motion control networks employ a precise, time synchronized exchange of data between a controller and multiple drive devices in order to achieve high performance coordinated motion. Traditional network solutions use a time slot approach where the network update cycle is divided into time slots. Each node within the network then utilizes a corresponding assigned time slot to transmit its data.
Utilization of the time slotting approach is problematic when employed in connection with an open standard network such as Ethernet. For example, restricting when a node can communicate over the network violates standard Ethernet protocol, and thus, typically requires these motion control protocols to either remain isolated from the general network or apply a gateway device. Additionally, the time slot protocols require extensive configuration and arbitration to setup and are typically not able to be modified while the network is operational. Thus, nodes cannot be added or removed from the network during runtime, which leads to costly downtime associated with updating the network. Further, devices adopting a time slot protocol are constrained to operate in synchrony with a controller's update cycle; thus, a drive device is constrained to a set of update frequencies that are an integer multiple of the controller's update period.
Traditional motion control techniques additionally do not allow communication of non-motion control data over the network, since the time slotting methods tend schedule the network's entire bandwidth. Conventional motion control network protocols can configure or negotiate a specific time slot for each drive node to send its actual data and then a time slot for a controller to send command data. According to some protocols, a portion of the update cycle can be reserved for passing non-motion control data. However, non-motion nodes typically cannot coexist on the network since they would interfere with transmissions associated with the motion specific time slot scheduling. Thus, non-motion messages can only be passed through the network via a gateway that delays its transmission until the non-motion message time slot is available.
Moreover, motion control networks have conventionally been constrained by data structures that are fixed in size and content. Such constraints are due in part to the time slot protocols used by these networks to provide time synchronization and deterministic data transfer. If a data structure exceeds the size limit associated with the associated time slot, the transmission may collide with data from a network node assigned to the next time slot. Current motion control protocols define fixed size data structures at configuration time that typically cannot be changed at runtime, since the time slotting is determined based on the size of the data packets passed between the drive(s) and controller nodes. Accordingly, network bandwidth is wasted due to the data packets oftentimes being an improper size (e.g., if a data packet is too large then extra “pad” data is transmitted over the network, if a data packet is too small then multiple transmissions may be required to convey the data).